Remove relays that fail to rotate onion keys from the consensus
On legacy/trac#7164 (moved), a cypherpunks notes that Backlog relays fail to rotate their onion keys. This should be addressed by identifying these relays, and adding them to the DirAuths' AuthDirInvalid or AuthDirReject lists.
First, we need to update torspec/dir-spec.txt to say that relays SHOULD rotate their onion keys every 7 days, and MUST rotate them every N days. (I suggest 14 or 28.)
Then we can modify DocTor to check for relays in the consensus that have had the same onion key for N days. (I think DocTor is the right place for this check.)
This won't catch cases where relays repeat onion keys, but it will suffice to catch the most obvious misconfiguration - a read-only onion key file.